[AMQ-9646] Support selecting specific messages for command line backup

[mattrpav]

Example usage:

./bin/activemq backup --filename=backup.tar.gz --indexes=0,1,5,7,1000,1001     

[cshannon]

I don't really get the use case to be giving specific index values from the order index. How would people know what index to use for the messages they want?

It would seem much more beneficial to use something like message ids to find the messages to backup.

[mattrpav]

@cshannon indexes are handy when performing surgery to get specific messages out (may already know position based on browse or console UI), or when a user wishes to get the last message off the queue.

MessageId based is a good idea, that has been added in the latest commit.